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Need DAC w/output decoupling. Advice please

post #1 of 10
7/26/10 at 7:38am
Thread Starter 

Hi guys

 

Really need some assistance here.. breaking my head over this one. I have zero electronics knowledge so please talk to me in laymen's terms. Much appreciated :)

 

I have a Burson PI-100 integrated stereo amp. I watch movies on this thing, so I feed it DTS downmixed to stereo from my EMU 0404 PCI. I guess the downmixing codec isn't perfect, because it causes the amp to jump into protection mode, probably due to the subwoofer channel causing some kind of DC leakage into the amp (which shouldnt happen in a perfect downmixing situation).

 

I talked to Burson and they recommended I put some 10uF caps between the RCA and the PCB, which I tried and it didnt solve the problem (as input caps. I used Vishay MKT1813 I think if that matters). Does anyone know of any decent DAC that has output decoupling that will solve my problem? :( I watch a lot of movies on my stereo system and this really ruins the experience. It jumps into protection mode a lot (and I have to stop the movie and reset the amp).

 

Thanks in advance

 

maxxy

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post #2 of 10
7/27/10 at 6:32am

You just said you installed some output caps and it didn't help your issue.

Are you sure you installed them correctly?

 

Output caps or inputs caps are exactly the same thing in a different circuit position.


Edited by ROBSCIX - 7/27/10 at 6:39am
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post #3 of 10
7/27/10 at 8:18am
Thread Starter 

Hi ROBSCIX

 

Well, Burson didn't really send me any schematics. They were archived and retrieving them would take "a few days" or so they say (hmpf...).

 

I connected the caps like this (didn't solder 'em because I wanted to make sure they work before soldering stuff to the amp):

 

RCA cable > 10uf cap > RCA cable  > Amp (Left channel)

and the same for the Right channel

 

According to the photos I sent Burson of my amp, that's the way they told me to connect it. Enclosed is the "detailed description" of how I should connect the amps (the arrows were added by the Burson techy):

 

4.jpg

 

When connecting one channel to the amp (either left or right), the dc protection wouldn't kick in. Connecting both (with or without caps) would cause the amp to jump.

 

I would still appreciate any solutions regarding either fixing the amp (I know this isn't the right forum for that, sorry) or if anyone can recommend a decent DAC which will solve my DC problems :(

 

Thanks in advance!


Edited by maxxy - 7/27/10 at 8:20am
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post #4 of 10
7/29/10 at 4:31am
Thread Starter 

shameless bump. advice please :(

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post #5 of 10
7/29/10 at 10:29am
Quote:
Originally Posted by maxxy View Post

(didn't solder 'em because I wanted to make sure they work before soldering stuff to the amp)


You have to disconnect the white wires and replace them with caps to do this test.

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post #6 of 10
7/30/10 at 2:22am
Thread Starter 

Hi

 

Thanks for the input. But why do I have to disconnect the white wires? Isn't doing what I did going to give the same effect?

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post #7 of 10
8/3/10 at 11:30am

The decoupling caps go right in the audio signal path.  The will block all DC and allow AC(audio signals) to pass through.

 

They are bad for the signal but sometimes needed.  However, doesn't your next device have decoupling on the inputs?

Many people will remove them from their sources as the receivers, amps..etc will in many cases have input decoupling caps so they are redundant and your just degrading the signal quality for nothing.

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post #8 of 10
8/5/10 at 11:10am
Quote:

Originally Posted by ROBSCIX View Post

 

However, doesn't your next device have decoupling on the inputs?

 


If I understand correctly, the Burson amp IS the next device and it was recommended that he install input coupling caps to remove DC offset and ultra-low frequencies coming from the DAC. For this to work, he has to REMOVE the white wires and replace with caps.

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post #9 of 10
8/6/10 at 4:55pm
Thread Starter 

Hi

 

Thanks for the replies. I was hoping that perhaps there is a DAC that will solve these issues for me and clean the sound for the amp (currently using a PCI EMU 0404).

I will try to install the caps instead of the wires and update.

 

Thanks

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post #10 of 10
8/7/10 at 10:16pm

IMO the PCI EMU 0404 is a good sound controller and DAC, but the software is not up to my standards. I don't know the true nature of your problems, but the cap mod is a good recommendation.

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